Scotland's Franchitti won the season title by default when the race was cancelled. But that was the last thing on his mind as he and fellow drivers somberly toured the course in a five-lap tribute to their fallen colleague.

Wheldon, a 33-year-old two-time winner of the fabled Indianapolis 500, died of injuries received when his car soared into the air and hit the catch fencing in the midst of a fiery 15-car crash on the 12th lap of the season-ending race at Las Vegas.

The packed field and the high speeds achieved on the 1.5-mile oval had sparked driver concerns even before the race, and Brazilian Tony Kanaan questioned the aggressive driving of some of his rivals.

"One mistake can take 15 people out, and that's what happened there," Kanaan said. "I've never seen such a mess in my entire career."

Wheldon's car was one of several that went airborne. Others erupted in flame, leaving a trail of smoldering debris on the track.

Wheldon was airlifted to hospital, but two hours after the race was stopped his fellow drivers learned the married father of two small sons had died.

He was the first IndyCar driver to die of on-track injuries since Paul Dana was killed in a pre-race practice crash in Florida in 2006.

"This is incredibly sad," Spanish driver Oriol Servia said. "We all know this is part of the sport.

"Cars are getting safer, tracks are getting safer, so fortunately it hasn't happened in a long time.

"We all had a bad feeling about this place in particular just because of the high banking and how easy it was to go flat," Servia added. "We knew it could happen, but it's just really sad."

Andretti Autosport, the team with which Wheldon won the Indy 500 in 2005, said they had agreed to a contract with Wheldon for 2012 -- a deal that was to be formalized after the race.

"Back when he was with the team in '05, we referred to the team as 'The Beatles' because it was such perfect harmony -- and with Dan coming back, there was talk of putting 'The Beatles' back together," said the team's marketing vice president John Lopes. "So today is devastating."

Asked about the circumstances that might have led to the crash, team owner Chip Ganassi said it was too soon to discuss that.

"There'll be plenty of time in the offseason to talk about that," Ganassi said. "Now is not the time to talk about that."

Franchitti added: "I agree. We'll discuss that and sort it out."

Franchitti was trying to remember good times he shared with Wheldon, but he admitted he was finding it tough going.

"I was thinking about old Dan stories and things that we did," Franchitti said. "I was thinking about some of the fun times we had. But really, right now it's just sad. It's just really, really sad.